Cantergiani said: "Almost everything is arranged. There are details that should not be a problem to solve. We still have to agree on the percentage Audax will receive in a second transfer, but all the rest is defined."
The Mendoza-born player is expected in London early next month to sign a five-year deal with Audax Italiano receiving seven million US dollars (around £3.5million).
"Chelsea have been following Franco for more than a year and negotiations have been quick," the player's agent Gustavo Goni commented.
"The club want to sign him in January when the transfer window opens."
Di Santo, meanwhile, refused to reveal details on this transfer: "My agent told me not to talk about this, but the truth is I won't go on playing at Audax. Playing at Chelsea would be very nice. It would be fantastic."